Layer composite and method for producing a layer composite

Abstract

Layered composite with three overlapping layers of metal, wherein an inner layer is arranged between two outer layers, wherein the inner layer is connected to each of the two outer layers in coupling surfaces by roll-bonding technology, and wherein separating layers are arranged outside the coupling surfaces between the inner layer and the respective outer layer, wherein a cavity structure formed by internal high-pressure forming is arranged in areas with the separating layers between the inner layer and each of the two outer layers, and a method for producing such a layered composite.

Description

[0001] The invention relates to a layered composite with three overlapping metal layers, wherein an inner layer is arranged between two outer layers, the inner layer being connected to each of the two outer layers at coupling surfaces by roll-bonding technology, and wherein separating layers are arranged between the inner layer and the respective outer layer outside the coupling surfaces, and wherein a cavity structure formed by internal high-pressure forming is arranged in areas with the separating layers between the inner layer and each of the two outer layers. The application further relates to a method for producing such a layered composite.

[0002] DD 269 204 A1 discloses a jacketed tube heat exchanger manufactured using a roll-bond process. The heat exchanger can be used as an evaporator or condenser in refrigeration applications. It consists of a continuously conically expanding inner channel surrounded by a conical outer channel with a constant flow cross-section. The heat exchanger is manufactured using the roll-bond process. The sheets to be joined are pre-structured with conical conductors and, after welding, expanded into conical channels.

[0003] The article “Roll Bonding Processes: State-of-the-Art and Future Perspectives” in Metals 2021, 11, 1344 by Khan, HA et al. concerns roll bonding, a manufacturing process in which plates or sheets are cold- or hot-rolled to join similar and dissimilar materials through the principle of strong plastic deformation. The review covers the mechanics of roll bonding processes and their key process parameters.

[0004] DE 10 2022 111 487 A1 discloses a temperature control element for a battery storage device, wherein the temperature control element comprises a first temperature control channel structure and at least one further temperature control channel structure, through which a temperature control medium can flow and which each comprise a main flow area that fluidically connects an inflow area and a return flow area, wherein the first temperature control channel structure and the at least one further temperature control channel structure form a base body that is at least partially multilayered. The multilayer base body has three components that are partially interconnected, wherein the first temperature control channel structure is bounded by two of the components and is provided on a top side of the base body, and the at least one further temperature control channel structure is bounded by two of the components and is provided on a bottom side of the base body.

[0005] One task may be to provide a layered composite or a process for producing a layered composite that enables simplified manufacturing and / or improved heat transfer.

[0006] The problem is solved by a layered composite according to claim 1 and by a method for producing a layered composite according to claim 10. Advantageous embodiments are specified in the dependent claims.

[0007] In this layered composite with three overlapping metal layers, an inner layer is sandwiched between two outer layers. The inner layer is bonded to each of the two outer layers at coupling surfaces using roll-bonding technology. Outside the coupling surfaces, separating layers are arranged between the inner layer and the respective outer layer. A cavity structure formed by internal high-pressure forming is located in the areas with the separating layers between the inner layer and each of the two outer layers, with at least one of the three overlapping layers differing in strength from the other layers. For example, the strength of the inner layer may be lower than that of the outer layers. At least one of the layers may consist of an aluminum-based alloy, in particular all three layers. The inner layer and the two outer layers may each have a minimum thickness of 0.5 mm, with the composite having a thickness between 1.5 mm and 5 mm.

[0008] The layered composite enables the production of a high-quality, functional 3D component using a simple manufacturing process with robust components and standard alloy concepts. The resulting hollow structure can be used in a variety of ways, for example, as media-carrying channels, spacers, connection points within a vehicle body, damping elements, or structural stiffeners. The layered composite is advantageously suited for use as a cooling plate for a rechargeable battery in an electric vehicle. Functions can thus be assigned to the layered composite, for example, in the areas of heat transfer, corrosion protection, surface finish, aerodynamics, acoustics, noise, vibration, harshness (NVH), energy absorption, and optics.

[0009] The strength of the layers is understood as their ability to withstand mechanical stresses before failure occurs. Failure can be an impermissible deformation, such as plastic deformation or fracture. Strength is the maximum mechanical stress that the respective layer withstands during its deformation. More specifically, the strength of the layers can be, for example, tensile strength, compressive strength, flexural strength, torsional strength, and / or shear strength. Tensile strength, for instance, is the maximum tensile stress that a material can withstand. The layer with lower strength is advantageously easier to process using internal high-pressure forming. The overall strength of the layered composite is ensured, for example, by the other layers with higher strength.The strength of the layer or layers with higher strength can, for example, be at least twice as great as the strength of the layer or layers with lower strength.

[0010] According to one embodiment, the adhesive strength of the bonds formed in the coupling surfaces is greater than the tensile strength of the layer with the lowest tensile strength. The adhesive strength characterizes the adhesion of the layers to one another. It can be determined in a peel test, in which, for example, one of the layers is deflected by a roller perpendicular to a plane defined by the layers using a tensile testing machine. The adhesive strength is limited by the tensile strength of the layer being peeled off. If the adhesive strength of the bonds is greater than the tensile strength of the layer with the lowest tensile strength, then the layer with the lowest tensile strength will tear in the tensile test even before reaching the tensile force required to peel off a layer.

[0011] According to a further embodiment, at least one of the outer layers forms a flat surface; in particular, both outer layers can each form a flat surface. The cavity structure can have at least two separate cavities, which can be arranged, in particular, at least partially in a common plane. The cavities can be separated from each other by the inner layer.

[0012] According to a further embodiment, the coupling surfaces of the two outer layers can be arranged asymmetrically with respect to a central plane of the layered composite. On at least one of the outer layers, the ratio of the coupling surfaces to the area of ​​the separating layers can be at least 0.3, preferably at least 0.35, and particularly preferably at least 0.4.

[0013] According to another embodiment, the separating layers of the two outer layers can be arranged to overlap in sections. For example, the separating layers overlap over at least five percent of the surface area of ​​the layered composite.

[0014] Another aspect concerns the process for manufacturing a layered composite consisting of three overlapping metal layers, wherein an inner layer is positioned between two outer layers. The strength of at least one of the layers differs from that of the other layers, for example, being lower. The inner layer is bonded to each of the two outer layers at coupling surfaces using roll bonding. Outside these coupling surfaces, separating layers are placed between the inner layer and the respective outer layer. A cavity structure is formed in the areas containing the separating layers between the inner layer and each of the two outer layers by internal high-pressure forming. The strength of the layers can be, more specifically, tensile strength, compressive strength, flexural strength, torsional strength, and / or shear strength.Tensile strength, for example, is the maximum mechanical tensile stress a material can withstand. Each layer with lower strength is advantageously easier to process using internal high-pressure forming. The overall strength of the layered composite is ensured, for example, by each layer with higher strength. The strength of the layer(s) with higher strength can, for instance, be at least twice as high as the strength of the layer(s) with lower strength.

[0015] In the production of a layered composite, the layers can be processed, for example, in the form of strip material unwound from coils. In roll-bonding technology, the strips are joined together by rollers under high pressure through a process called pressure bonding. Optionally, the material can be preheated. The separating layer prevents the strips from bonding in certain areas. The layered composites are then separated, a process that can generally be carried out before the sheets are joined.

[0016] In internal high-pressure forming, high pressure is introduced through an opening into the area containing the separating layer by forcing a fluid, such as compressed air, water, or oil, under pressure into the opening. This causes the areas of the layers that are not bonded due to the separating layer to expand, forming the cavity structure. After the cavity structure has formed, the pressure is released.

[0017] According to one embodiment, all three layers are rolled simultaneously during the joining process, with the three layers being rolled in particular with a total rolling rate of at least 40%.

[0018] According to an alternative embodiment, in the joining process an outer layer is first rolled with the inner layer as an intermediate composite and then the further outer layer is rolled with the intermediate composite, wherein in particular both rolling processes are carried out with such degrees of reduction that an overall degree of reduction of at least 40% is achieved.

[0019] According to another embodiment, the layers can be heated to a temperature between 200°C and 550°C before bonding. The separating layer, applied for example by screen printing, then diffuses into the material. The surfaces of the layers to be bonded can be roughened and cleaned by brushing before bonding. After bonding, the layers can be recrystallized by annealing and then cooled.

[0020] The invention is explained in more detail below with reference to the accompanying drawings. The explanations relate to both the layered composite and the method for its production. The figures show Fig. 1. An embodiment of the layered composite in successive stages of the manufacturing process; Fig. 2 another embodiment of the layered composite in successive stages of the manufacturing process; Fig. 3 another embodiment of the layered composite in successive stages of the manufacturing process; Fig. 4. An embodiment of the method is shown using a schematic flowchart; Fig. 5. Another embodiment of the method is shown using a schematic flowchart; Fig. 6 another embodiment of the layered composite.

[0021] In the Fig. Figure 1 schematically depicts an embodiment of the layered composite in successive stages a, b, and c of the manufacturing process. The layered composite comprises three overlapping layers 10, 12, 14 made of metal, with an inner layer 12 arranged between two outer layers 10, 14. The inner layer 12 is bonded to each of the two outer layers 10, 14 in coupling surfaces 32 by roll-bonding. Outside the coupling surfaces 32, separating layers 34 are arranged between the inner layer and the respective outer layer. The tensile strength of the inner layer 12 is lower than the tensile strength of the outer layers 10, 14. Stage a shows the layers 10, 12, 14 before bonding with the applied separating layers 34. Stage b shows the bonded layers 10, 12, 14 after bonding by roll-bonding. The layered composite is manufactured, in particular, as a continuous process.The adhesive bond between layers 10, 12, and 14 is created by a hot or cold rolling process. In this process, also known as roll cladding, the three layers 10, 12, and 14 are mechanically joined or interlocked under the influence of a rolling force and / or, with the additional application of heat, undergo a diffusion-supported adhesive bond. The adhesive strength of the bonds created in the coupling surfaces 32 can be, in particular, greater than the tensile strength of the layer with the lowest tensile strength, in this case, the inner layer 12.

[0022] Subsequently, a cavity structure 25 is formed in the areas with the separating layers 34 between the inner layer 12 and each of the two outer layers 10, 14 by internal high-pressure forming. The cavity structure 25 has two separate cavities 25A, 25B. Stage c shows the layered composite with the first and second cavities 25A, 25B. Both outer layers 10, 14 form a flat surface. The flat outer surfaces of the outer layers 10, 14 can advantageously be used as a contact or assembly surface. The cavities 25A, 25B can be arranged at least partially in a common plane and are separated from each other by the inner layer 12. The coupling surfaces 32 of the outer layers 10 and 14 are arranged asymmetrically with respect to a central plane of the layered composite, the central plane of the layered composite being understood as a plane located midway between and parallel to the outer layers 10 and 14.In a top view, the coupling surfaces 32 of the outer layers 10, 14 are arranged at least partially offset from one another. The ratio of the coupling surfaces 32 to an area of ​​the separating layers 34 is at least 0.3, preferably at least 0.35, and particularly preferably at least 0.4 on each of the outer layers 10, 14.

[0023] In the Fig. Figure 2 schematically depicts another embodiment of the layered composite in successive stages a, b, c, and d of the manufacturing process. Stage a shows layers 10, 12, and 14 before bonding with the applied separating layers 34. Stage b shows the bonded layers 10, 12, and 14 after bonding by roll-bonding. The ratio of the bonding areas 32 to the area of ​​the separating layers 34 is significantly larger for the upper outer layer 10 than for the lower outer layer 14. The internal high-pressure forming of the cavity structure 25 in the areas with the separating layers 34 is carried out in two steps. First, the second cavity 25B is formed between the inner layer 12 and the upper outer layer 10, as shown in stage c. The first cavity 25A is then formed between the inner layer 12 and the lower outer layer 14, as shown in stage d.In the exemplary embodiment of the layered composite, the outer layers 10, 14 can, for example, be shaped according to their respective functions. The geometries of the two outer layers 10, 14 are advantageously independent of each other. Both cavities 25A, 25B, or even just one, can be designed to carry the medium. The cavity structure 25 can also act purely as an energy absorber or serve as a connection or spacing point.

[0024] In the Fig. Figure 3 schematically illustrates another embodiment of the layered composite in successive stages a, b, c, and d of the manufacturing process. Stage a shows the layers 10, 12, and 14 before bonding with the applied separating layers 34. Stage b shows the bonded layers 10, 12, and 14 after bonding by roll-bonding. The ratio of the bonding areas 32 to the area of ​​the separating layers 34 is significantly larger for both outer layers 10 and 14 than in the embodiment according to Figure 3. Fig. 1. The internal high-pressure forming of the cavity structure 25 in the areas with the separating layers 34 is carried out in two steps. First, the first cavity 25A is formed between the inner layer 12 and the lower outer layer 14, whereby the upper outer layer 10 is also deformed, as shown in stage c. The second cavity 25B is then formed between the inner layer 12 and the upper outer layer 10, as shown in stage d. The lower outer layer 14 forms a flat surface. The representation of the Fig. 1 to 3 is schematic and does not take into account, for example, dimensional changes of layers 10, 12, 14 due to the rolling process.

[0025] The Fig. Figure 4 shows an embodiment of the method for producing a layered composite using a schematic flowchart. The arrows illustrate the process. Three overlapping layers 10, 12, 14 made of metal are provided, with an inner layer 12 positioned between two outer layers 10, 14, and the tensile strength of the inner layer 12 being lower than that of the outer layers 10, 14. In a first step, the surfaces 16 of the three metal layers 10, 12, 14 to be bonded can be surface-treated by rotating brushes 42. This is intended to give the pre-treated surfaces 16 a uniform, rough surface. In the next process step, the separating layer 34 is applied to defined areas of the pre-treated surfaces 16 of the outer layers 10, 14, for example, by screen printing. Alternatively, the separating layer 34 can be applied to the inner layer 12.Subsequently, all three layers 10, 12, 14 are heated in a heat treatment device 44. Before joining, the layers are heated to a temperature between 200°C and 550°C, for example. The inner layer 12 is then joined to each of the two outer layers 10, 14 at the coupling surfaces 32 by roll bonding, for example, by rolling the layers 10, 12, 14 together through rollers 46A, 46B, in particular with a reduction of at least 40%, to form a composite. The dimensional change due to rolling is not shown graphically. After rolling 46A, 46B, the layers 10, 12, 14 are recrystallized by annealing in a heat treatment device 44 and subsequently cooled in a cooling device 48.A cavity structure 25 is formed in the areas with the separating layers 34 between the inner layer 12 and each of the two outer layers 10, 14 by internal high-pressure forming, in which fluid media 52A, 52B are injected into the separated areas 34 between the layers in a final step, so that the areas are formed into cavities 25A, 25B.

[0026] The Fig. Figure 5 shows an embodiment of the method for producing the layered composite by means of a schematic flowchart, wherein, in the joining process, one of the outer layers 10 is first rolled with the inner layer 12 to form an intermediate composite 18, and subsequently the other outer layer 14 is rolled with the intermediate composite 18. In the first step, the surfaces 16 of the two of the three layers 10, 12 to be joined are surface-treated by the rotating brush 42. The pre-treated surfaces 16 thus advantageously acquire a uniform, rough surface. In the next process step, the release agent 34 is applied to defined areas of the pre-treated surface 16 of one of the layers, for example, the outer layer 10. Subsequently, both layers 10, 12 are heated in a heat treatment device 44 and then rolled by the rollers 46A, 46B with a reduction of at least 40% to form the intermediate composite 18.After rolling by rollers 46A and 46B, the bonded layers 10 and 12 are recrystallized by annealing in a heat treatment unit 44. After cooling, the surfaces 16 to be bonded are roughened again by surface treatment 42 to form the bond between the third layer 14 and the intermediate layer 18. Subsequently, for example, the separating layer 34 is applied to the individual outer layer 14. In the next step, all layers 10, 12, and 14 are heated in a heat treatment unit 44 and then rolled by rollers 46A and 46B with a minimum reduction of 40% to form a three-layer composite. After rolling by rollers 46A and 46B, the bonded layers 10, 12, and 14 are recrystallized by annealing in a heat treatment unit 44 and then cooled in a cooling unit 48.The cavity structure 25 is formed in the areas with the separating layers 34 between the inner layer 12 and each of the two outer layers 10, 14 by internal high-pressure forming, in which fluid media 52A, 52B are injected into the separated areas 34 between the layers in a final step, so that the areas are formed into cavities 25A, 25B.

[0027] In the Fig.Figure 6 shows a further embodiment of the layered composite in a perspective sectional view. The cavity structure 25 has two separate cavities 25A, 25B. Both outer layers 10, 14 form a flat surface. The separating layers 34 of the outer layers 10, 14 overlap each other by at least five percent. The material of the outer layers 10, 14 can have a yield strength Rp0.2 of at least 40 MPa, a tensile strength Rm of at least 80 MPa, an elongation at break A50 of at least five percent, and a thickness of at least 0.4 mm. The material of the inner layer 12 can have a yield strength Rp0.2 of at least 20 MPa, a tensile strength Rm of at least 40 MPa, an elongation at break A50 of at least 20 percent, and a thickness of at least 0.2 mm. Reference symbol list 10 Location, external location 12th layer, inner layer 14 Location, external location 16 surface 18 Intermediate connection 32 coupling area 34 Separation layer 25 Cavity structure 25A First cavity 25B Second cavity 42 brushes 44 Heat treatment 46 rollers 48 Cooling 52A, 52B Media QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DD 269 204 A1

[0002] DE 10 2022 111 487 A1

[0004] Cited non-patent literature

[0000] Roll Bonding Processes: State-of-the-Art and Future Perspectives” in Metals 2021, 11, 1344 by Khan, HA

[0003]

Claims

[1] Layered composite with three overlapping layers (10, 12, 14) of metal, wherein an inner layer (12) is arranged between two outer layers (10, 14), wherein the inner layer is connected to each of the two outer layers in coupling surfaces (32) by roll-bonding technology and wherein separating layers (34) are arranged outside the coupling surfaces between the inner layer and the respective outer layer; wherein a cavity structure (25A, 25B) formed by internal high-pressure forming is arranged in areas with the separating layers (34) between the inner layer (12) and each of the two outer layers (10, 14), where the strength of the inner layer (12) is lower than the strength of the outer layers (10, 14) wherein at least one of the three overlapping layers (10, 12, 14) differs in strength from the other layers. [2] Layer composite according to claim 1, characterized by, that at least one of the three overlapping layers (10, 12, 14) differs from the other layers in its tensile strength. [3] Layer composite according to claim 2, characterized by , that the bond strength of the connections produced in the coupling surfaces (32) is greater than the tensile strength of the layer with the lowest tensile strength. [4] Layer composite according to one of the preceding claims, characterized by , that at least one of the outer layers (10, 14) forms a flat surface, in particular that both outer layers each form a flat surface. [5] Layer composite according to one of the preceding claims, characterized by , that the cavity structure (25) has at least two separate cavities (25A, 25B). [6] Layer composite according to one of the preceding claims, characterized by, that the cavities (25A, 25B) are arranged at least sectionally in a common plane, wherein the cavities (25A, 25B) are separated from each other in particular by the inner layer (12). [7] Layer composite according to one of the preceding claims, characterized by , that the coupling surfaces (32) of the two outer layers (10, 14) are arranged asymmetrically with respect to a central plane of the layer composite. [8] Layer composite according to one of the preceding claims, characterized by , that the separating layers (34) of the two outer layers (10, 14) are arranged in a section-by-section overlapping manner. [9] Layer composite according to one of the preceding claims, characterized by , that at least one of the layers (10, 12, 14) consists of an aluminum-based alloy. [10] Method for producing a layered composite of three overlapping layers (10, 12, 14) of metal, wherein an inner layer (12) is arranged between two outer layers (10, 14), wherein the strength of at least one of the layers (10, 12, 14) differs from that of the other layers, wherein the inner layer (12) is connected to each of the two outer layers (10, 14) in coupling surfaces (32) by roll bonding technique, and wherein separating layers (34) are arranged outside the coupling surfaces between the inner layer and the respective outer layer, wherein a cavity structure (25) is formed in areas with the separating layers between the inner layer and each of the two outer layers by internal high-pressure forming. [11] Method according to claim 10, characterized by , that during the joining process all three layers (10, 12, 14) are rolled simultaneously. [12] Method according to one of the preceding claims 10 or 11, characterized bythat the three layers (10, 12, 14) are rolled with a total rolling rate of at least 40%. [13] Method according to any one of the preceding claims 10 to 12, characterized by , that in the joining process one of the outer layers (10, 14) is first rolled with the inner layer (12) as an intermediate composite (18) and subsequently the further outer layer is rolled with the intermediate composite. [14] Method according to any one of the preceding claims 10 to 13, characterized by that in both rolling processes, a total rolling rate of at least 40% is achieved. [15] Method according to any one of the preceding claims 10 to 14, characterized by that the layers are heated to a temperature between 200°C and 550°C before being joined. [16] Method according to any one of the preceding claims 10 to 15, characterized by , that the surfaces (16) of the layers to be joined are roughened and cleaned by brushing before joining.

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